1. Field of the Invention
The present invention relates to medical devices. More particularly, the present universal passive protector for an IV catheter relates to intravenous catheters designed to protect medical personnel from accidental impalement and possible infection.
2. Description of the Related Art
Medical professionals commonly use intravenous needles to insert and withdraw fluid from patients. However, when introducing or withdrawing large amounts of fluid, such that the intravenous device is disposed within the vein for an extended period of time, metal needles are disadvantageous because their rigid structure and sharp distal tip can cause trauma to the patient's vein. Thus, medical professionals commonly use a catheter for such applications.
A catheter typically comprises a flexible tube having a soft tip. Catheters are generally inserted into the patient's vein using a catheter introduction device. A first type of introduction device comprises a through-the needle catheter, which is inserted into an anatomical passage through the use of a cannula. The cannula itself typically comprises an elongate, metal needle which punctures the skin, tissue and vein wall to provide a path for placement of the catheter in the vein. When the needle pierces the vein, blood will “flashback” through the needle and into a flashback chamber typically located at the proximal end of the needle. Thus, once the medical technician observes this “flashback” of blood, the medical technician will know that the needle has been inserted into the vein. The catheter is then advanced through the interior of the needle and into the passage. Once the catheter is properly inserted into the passage, the needle is withdrawn from the patient and the catheter can be advanced further into the vein.
A second type of introduction device comprises an over-the-needle catheter system. In such over-the-needle catheter systems, a thin catheter having a hub attached to its proximal end is advanced over a rigid cannula, such as a needle, with the cannula and catheter being simultaneously inserted into a desired anatomical passage of a patient. Once the cannula and accompanying catheter have been introduced into the passage, which is typically indicated by a flashback chamber filling with blood, the cannula is withdrawn from within the catheter interior, thus leaving the catheter operatively disposed within the passage. Thereafter, a hub mounted to the proximal end of the catheter may be used to fluidly connect the same to an infusion line or device.
However, once the catheter has been inserted into the anatomical passage, the cannula can typically only be removed from therewithin by retracting the same upwardly along the catheter, thereby undesirably exposing both the patient and the attendant medical personnel to accidental contact with the cannula, and more particularly the piercing tip of the needle. In recent years, concern over such accidental needlesticks has become more pronounced because of the advent of currently incurable and fatal diseases, such as Acquired Immune Deficiency Syndrome (“AIDS”), which can be transmitted by the exchange of bodily fluids from an infected person to another person. A needle that has been used to place a catheter in the vein of an AIDS infected person is a vehicle for transmission of the disease. Thus, it is advantageous to cover a needle immediately after use to avoid needlesticks.
A number of protective devices have been developed recently to help reduce the incidence of disease transmission through needlesticks. Some of these devices comprise an elongate sheath into which the needle advances as it is withdrawn from the patient. When the needle is completely withdrawn, its sharp distal tip is safely enclosed within a wider tube, which is usually made of plastic. Generally, a locking mechanism prevents the needle from exiting the sheath.
U.S. Pat. Nos. 4,762,516 and 4,950,252 disclose examples of typical protective devices for use with an over-the-needle catheter. The devices described in these patents each comprise a hub attached to the proximal end of the catheter. A proximal end of the hub is in turn connected to a distal end of an elongate sheath via a friction fit. The sheath is a tube, usually plastic, having a rectangular cross-section and a hollow cavity enclosed by sidewalls. Other similar devices may have different cross-sections, such as round or octagonal. A slider disposed about the outside of the sheath is attached to the proximal end of the needle. The slider may be attached to the needle through a hole in a proximal end of the sheath, or through a longitudinal slit in a sidewall of the sheath. A proximal portion of the sheath includes a pair of oppositely-disposed outwardly-biased tabs. A distal portion of an inside surface of the slider includes a pair of indentations configured to matingly receive the tabs.
With the slider positioned about the distal end of the sheath, the sharp distal tip of the needle protrudes from the distal end of the catheter. After insertion of the needle into the patient's vein, the slider is moved toward the proximal end of the sheath, thereby drawing the needle out of the patient's vein and leaving the catheter disposed within the vein. As the slider nears the proximal end of the sheath, and the distal tip of the needle nears the distal end of the sheath, the inside surface of the slider maintains the tabs inwardly of the slider. As the distal tip of the needle enters the distal end of the sheath, the indentations on the inside surface of the slider reach the outwardly biased tabs on the sheath. The tabs snap into the indentations, locking the relative positions of the slider and sheath. The sharp distal tip of the needle is thus safely locked within the sheath. When the needle is safely stowed, the hub is removed from the sheath, and is ready to receive an injection/aspiration device.
Device like those described in the '516 and '252 patents, however, are prone to leaving the sharp distal tip of the needle exposed. The friction fit between the hub and the distal end of the sheath is unreliable. During catheter emplacement with one of these devices, the hub frequently disengages the sheath before the needle is completely retracted within the sheath. Of course, when the sharp needle tip exits the protective catheter before it enters the protective sheath, it could stick the operator or the patient.
Another type of protective device for use with an over-the-needle catheter is disclosed in U.S. Pat. Nos. 4,790,828, 4,978,344, 4,994,041 and 5,312,371. Devices of the type described in these patents comprise a needle assembly including a body or handle and an elongate needle extending from a distal end of the body. A cap, through which the needle passes, is secured to a distal end of the body, usually by a friction fit. A catheter hub is friction fit over the cap, and the catheter extends from a distal end of the hub and envelops the needle.
Upon inserting a distal tip of the catheter into a patient's vein, a medical professional grasps the catheter assembly and dislodges the friction fit between the cap and the body while withdrawing the needle from the catheter. The catheter hub and cap, which are friction fit together, thus move toward the distal tip of the needle. The cap pulls a capping mechanism, such as a tether cord or accordian-style sheath, along with it. When the cap reaches the distal tip of the needle, the capping mechanism becomes taut. Further withdrawal of the needle from the cap/catheter releases the friction fit between the cap and catheter hub. The cap thus covers the needle distal tip and the catheter is positioned in the patient's vein for use.
Like the devices described in the '516 and '252 patents, devices of the type described in the '828, '344, '041 and '371 patents cause needle sticks when the friction fit between the cap and catheter hub comes loose before the cap reaches the needle distal tip. These devices demonstrate that relying on a friction fit to prevent needle sticks is very risky. If the friction fit it too loose, the likelihood of a needle stick is high. If the friction fit is too tight, the device is difficult for a medical professional to manipulate.
U.S. Pat. Nos. 4,747,831 and 6,090,078 disclose examples of another type of protective device for use with an over-the-needle catheter. This type of device comprises a catheter having a hub attached to its proximal end. The needle is mounted at its proximal end to a piston. The piston is in turn mounted within a cylinder, which is a hollow plastic tube that is open at a distal end. The piston is biased toward a proximal end of the cylinder by a spring. In a pre-emplacement configuration, however, the piston is secured at the distal end of the cylinder by a latch attached to an external button. The needle thus protrudes from the distal end of the catheter.
After inserting the catheter into a patient's vein, a medical professional presses the button, releasing the spring and causing the needle to retract within the cylinder. The sharp distal tip of the needle is thus safely enclosed within the rigid plastic sheath. Depressing the button also releases the hub from the cylinder. The hub is thus ready to receive an injection/aspiration device.
Disadvantageously, devices of the type described in the '831 and '078 patents often malfunction. The button used to retract the needle is very sensitive. Thus, the medical professional often depresses the button accidentally before the catheter is properly emplaced. Such accidental activation is unlikely to result in a needle stick, but it usually causes the catheter to become contaminated. When the hub is released without the distal end of the catheter safely inserted into the patient's vein, the catheter is unrestrained and usually falls to the floor. Upon contact with the floor or other non-sterile surface, the catheter must be discarded. The operator must then perform the procedure again using a new device. Thus, these devices generate a great deal of waste, both of material and of time. Further, if the operator pierces the patient's skin before accidentally activating the device, the patient must endure multiple needle sticks in order to have a catheter emplaced in his or her vein.
U.S. Pat. No. 5,718,688 describes still another type of protective device for use with an over-the-needle catheter. The device comprises a catheter having an axial bore, a catheter hub at one end of the catheter, an introducing needle having a sharp distal tip, and a needle hub on the needle remote from the distal tip. Instead of an elongate plastic tube enclosing the entire needle, this device includes only a needle tip protector on the needle for shielding the needle tip when the needle has been withdrawn from the catheter bore. The needle tip protector includes a locking device which is initially in an unlocked position, permitting withdrawal of the needle from the catheter bore. Upon withdrawal of the needle from the catheter bore, the protector springs into a locked position, in which the locking device engages the outer surface of the needle and shields the sharp distal tip. The locking device retains the catheter hub on the needle when the locking device is in the unlocked position and releases the catheter hub from the needle when the locking device is in the locked position. Separation of the catheter from the needle is therefore prevented until the needle has been withdrawn from the catheter bore to trigger shielding of the needle tip.
Devices like the one described in the '688 patent, however, suffer from a number of drawbacks. First, these devices cover only the needle tip, and not the entire needle. During catheter insertion, however, portions of the needle other than the tip may become coated with blood. When exposed to medical personnel, this blood presents a safety hazard.
Second, these devices rely on friction to be effective. When the protector springs to the open position, locking cams engage the needle. The locking cams pinch the needle to secure the protector from being pulled off the distal end of the needle. The frictional force generated by the pinching locking cams, however, is relatively weak. Thus, the protector is rather easily pulled off the needle distal end, leaving the contaminated needle exposed.
Third, the protectors of these devices are very complex, and involve delicate moving parts. Consequently, they are difficult and expensive to manufacture, and prone to sudden failure. The embodiment of FIGS. 1 and 2, for instance, comprises a locking cam that is connected to one of the locking parts by a flexible hinge portion that is nothing more than a razor thin segment of plastic. A minor manufacturing defect in this critical portion of the protector could easily lead to failure and consequent exposure of medical personnel to a contaminated needle.
Thus, a passive protector for an IV catheter that is simply and cheaply constructed, completely encloses a used needle, and prevents needle sticks in a virtually foolproof manner without generating a large amount of waste, would be of great benefit to the healthcare profession.